Blimey, got my new PC up and running and found my way back to the forum.

Had the tree doctor in and reduced height of trees so am one step further forward towards goal of PV array and stonkin' battery storage using LiFeYPO4. Still struggling with all things Lithium, but have found a company called Balqon in the USA that sells Energy Storage Systems (battery banks) in a box with cell balancing and BMS spaghetti all pre attached. And the price for a 16kWh job, $8225.00 . Now divide by 3 multiply by 2 = £5483.33 + shipping + tax etc etc. Maybe £8K still waiting for email to confirm.

This is what I've been looking for. A decent price for decent gear for someone with not enough knowledge to be wiring up cell balancing/management stuff.

Mr Winston Chung (of Winston Thunder Sky etc) is involved in the company so they should know what they are talking about.

A typical LiFePO4 12v 200A = 2.4kWh battery in a well known blue box bought in the UK costs £2K.

A typical LiFePO4 yellow battery bank of 8 x 3v 1000A = 24kWh not in a box from mainland Europe costs around £6.4K with cell management and balancing as a DIY add on requirement + shipping.

So just thought you might want to check Balqon out.

£500/kWh, not bad.
What is the cycle life of these batteries?

Blue box is Victron I believe.

Had no answer as yet as to total cost or whether the batts are balanced etc before shipping. I suspect that taxes are pretty nasty ie vat and import duty = 30% plussage.

Cycle life is allegedly 3000 to 7000 depending on how they are used, all very approximate and unknown in reality.

I'll just have to wait and see.

Aren't NiFe cells very inefficient, though? AIUI they charge at a significantly higher voltage than they discharge so, though you get most of the amp·hours back out, you only get a relatively small proportion of the joules. If the cost per kWh stored over the lifetime is sufficiently low then this might be acceptable but it needs to be taken into consideration for complications like inverter input voltage ranges. It'd be interesting to know if anybody is actually using these for off-grid domestic use.

Yup, be interested to see how you get on with this one Dickster. Me, I'm a bit of a Luddite and stick with what I know for my 'off grid' properties. That will be the trusty old FLA, I've tried NiFe Willie and wasn't impressed, didn't seem to work very well the the inverter/chargers at the time and horribly inefficient. Having said that they seem to last forever and can take 'dogs abuse'.
Having explored all options in our 'off grid' new build, that will be totally powered by wind,sun, and water I went for FLA, but having worked with huge banks (.8mgWh) of LiFePO4 this last 17 months on our hybrid ferry, I'm severely impressed.
Sure, there have been a few issues with the BMS, and yes, it is horribly complex but they still remain a staggeringly impressive 98% efficient. These are not figures 'plucked out of a hat' but measured with proper calibrated instruments.
I'm pretty chuffed with my 800ah FLA bank for £3k but I'd be seriously looking at lithium when they need replacing.

Good luck, Paul

Thanks SteveZ - interesting thread. Bit distressed by the first post which seemed a bit confused on what a watt is (why do people find this so hard?) but the rest made more sense. Useful to see his confirmation of the problem of the discrepancy between the charge and discharge voltage.

Seem to be roughly the same price as LiFeYPO₄ - around £0.40/Wh.

Sometimes people worry about the complexity of LiFe[Y]PO₄ cells. As far as I can see [¹] they're quite simple and not much different from lead acid:

1) Don't over discharge them.
2) Don't overcharge them.
3) Once they're charged stop charging them.

The difference is that for LiFePOâ‚„ they really mean it. Lead acid will have its life shortened by overdischarge. LiFePOâ‚„ will be destroyed. Lead acid cells will tolerate a bit of overcharge and, for wet (as opposed to gel, etc) will actually benefit from a bit of bubbling once in a while to keep the liquid stirred up. Lead acid can be left on trickle charge once they're full but LiFePOâ‚„s hate it.

On the other hand, lead acid cells need to be kept full and any time they spend standing less than fully charged reduces their life whereas LiFePOâ‚„ can, and actually prefer, to be left somewhat discharged so long as they're not left so long that their (slow) self-discharge results in them over-discharging. In this respect LiFePOâ‚„ are much more suited to off-grid use.

The consequence is that you really need to monitor the voltage of each cell in a LiFePOâ‚„ battery and stop discharging when the weakest one is getting low and stop charging when the strongest is full. To get the maximum capacity out of the battery you therefore want the cells to be reasonably well balanced. On the other hand, if the cells are a bit out of balance it's not a disaster - it just means the usable capacity of the battery is reduced a bit until they're brought back into balance.

Many batteries made out of lots of small cells, as used in electric vehicles, have battery balancing built in. There's good experience, though, to indicate that batteries with small numbers of large cells in series don't really need this as they'll stay pretty much in balance for quite a lot of cycles if started off correctly. In fact, because the cells don't like to be trickle charged once full there's a positive advantage to not doing continuous balancing as this avoids the strongest cells being trickled while the weaker ones catch up.

Apart from needing voltage monitoring on each cell I don't think there's much more to running a LiFePOâ‚„ battery than a lead-acid one. The hassle is that most solar charge controllers and the like are set up for lead-acid and don't play well with LiFePOâ‚„.

[¹] That is, as far as I can see from copious reading of multiple sources and some playing with a few 20 Ah cells over a couple of years.

Dickster, might be worth talking to these people: http://www.sustainables4u.co.uk/TESS.php

They're mostly for on-grid storage (which I can't see the point of for an individual as the energy market is at the moment) but do mention off-grid.

Don't know where you are but I think you're less likely to have import duty or support issues with a company in West Sussex than one in the US.

Hi Dickster,

I would try and get a hold Peter Chow of 'Sustainables 4U' this is his forte and he does have a 'track record' with lithium. He quoted me for a 28kWh pack and charge control in 2012, it was in your 'ball park', in fact it was less, but that was three years ago using the now defunct Winston modules.

Good luck, Paul

I was in touch with Peter 18 months ago. Unfortunately, the 'Sustainables 4U' website doesn't suggest that too much is happening there at the moment and unfortunately this has instilled a lack of confidence in my wallet department (not necessarily justified). Geographically he is a bit too far away, meaning any problem solving might be logistically unviable.

Not sure if Winston is actually defunct or not.